#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n, p, u, m, x, i, s;

int calculeaza(int x){
    s=0;
    for(i=5; i<=x; i*=5)
        s+=x/i;
    return s;
}

int main(){
    f>>n;
    if(n==0)
    {
        g<<"1\n";
        return 0;
    }
    p=1;
    u=5*n;
    while(p<=u)
    {
        m=(p+u)>>1;
        x=calculeaza(m);
        if(x==n)
        {
            m=m-(m%5);
            g<<m<<"\n";
            return 0;
        }
        if(x<n)
            p=m+1;
        else
            u=m-1;
    }
    g<<"-1\n";
    return 0;
}